Internal combustion engine



FIG. 1 is a front view of an internal combustion engine showing our new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a front right perspective view thereof;

FIG. 8 is a front left perspective view thereof; and,

FIG. 9 is a rear left perspective view thereof. 

The ornamental design for an internal combustion engine, as shown and described. 